* virNetDevTapCreateInBridgePort() mock: free '*ifname' before
   strdupping a hardoded value to it
 * testCompareXMLToArgvFiles(): unref 'conn' object in cleanup
 * testCompareXMLToArgvHelper(): free 'ldargs' and 'dmargs' in
   cleanup

Commit c5b6a4a5 forget to update also this mock function.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

Commit b20d39a5 introduced a new argument for the
virNetDevTapCreateInBridgePort function, however, its mock
in bhyve tests wasn't updated, so the build failed.

Fix build by adding this new argument to the mock version.

At this point unittest covers 4 basic cases:

 - minimal working XML for bhyve
 - same as above, but with virtio disk
 - ACPI and APIC args test
 - MAC address test